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    SubjectRe: 3C905b partial lockup in 2.4.5-pre5 and up to 2.4.6-pre1
    Russell King wrote:
    > Indeed. However, I don't believe user space should _rely_ on the flag.
    > The reason is that there are network cards out there where the only way
    > to get the link status _is_ to transmit a packet, even on 10baseT.
    >
    > PCNET is one example - the "oh my god my link is down" status bit is in
    > the transmit ring headers, not in an easily accessible register.
    >
    > The only interpretation user space can place on IFF_RUNNING for these
    > cards is that if its not set, packets will get dropped by the interface.
    > If its set, packets _may_ be dropped by the interface.

    These are the exception not the rule, though, so I don't think we should
    design primarily for them. On most decent cards, we can not only ask
    for link status from a register, but also get interrupts when link
    change occurs [though we may still need a timer for certain link
    states].


    > [note I've not found anything in 2.4.5 where netif_carrier_ok prevents
    > the net layers queueing packets for an interface, and forwarding them
    > on for transmission].

    we want netif_carrier_{on,off} to emit netlink messages. I don't know
    how DaveM would feel about such getting implemented in 2.4.x though,
    even if well tested.

    Note we went over netif_carrier_xxx and related issues not a week ago,
    IIRC

    Jeff


    P.S. netdev@oss.sgi.com added to cc. please cc there on net
    interface/driver issues...

    --
    Jeff Garzik | Andre the Giant has a posse.
    Building 1024 |
    MandrakeSoft |
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